Laptop battery BMS

So I got a laptop, battery holds charge for like 5 minutes. I bought some 18650 batteries hoping to re-cell them. I think the BMS is one of those that shuts off if it loses power for any reason. During the move (I soldered to the new battery, then to the terminals on the BMS with the old battery attached) the power got cut off by accident and now the laptop refuses to recognize the battery as anything other than 0%.

When I ask (and there’s remarkably little info on laptop battery BMS) all they say is use those NALB1 battery thing which is quite expensive (I could buy a laptop for that price).

Do they make blank BMS that works with common laptop 8 pin connector, or do they make BMS that can output 19 volts so I can just plug that into the laptop’s AC jack instead?

It works without battery, but I like to be able to use it in places where I can’t plug in sometimes. Plus I need to do something with all the 18650 cells I wasted money on.

I think you’d be far better off asking this in a more specialized forum for… whatever it is you’re trying to do (repair/re-cell a laptop battery?), or even an appropriate sub on Reddit.

Somewhere that people discuss DIY electronics or laptop repair. It’s not really a question for a mostly English-language forum about Taiwan, IMO.

You should probably also specify the laptop and battery details. Also, no idea at all what you’re talking about here:

When you ask who? Who is “they”?

What is “those NALB1 battery thing”? “NALB1” doesn’t seem to be a common term for anything relating to batteries on Google — this post is close to the top of the search results.

(You don’t have to answer me here — I’m just saying in case you need to phrase things more clearly if you do ask the question somewhere more suitable.)

I don’t think anyone can help you here without having a look at the thing and poking around with a meter/scope. It’s not entirely clear what you’ve done or how the problem occurred (I’m not sure what “the power got cut off” means here). My best guess is that you’ve damaged the BMS by connecting the cells out of sequence - generally you should start from GND and work your way along the string to the highest-voltage cell when connecting the sense wires. The better BMS ICs are immune to this sort of thing, but it’s not guaranteed.

Your best bet here is (as you said) just connect your “new” battery to the AC jack. I’ve done this before and it works fine. It doesn’t have to be 19V. Most likely, if it’s 19V nominal, it will tolerate up to 22-23V at least. So what you want is 5 lithium cells in series (or maybe 5S2P if you have more than 5). Charge to the usual 4.2V/cell and you’ll be fine.

A BMS has multiple subsystems. The functions you need here are charge termination, low-voltage cutoff, and cell balancing. Modules that can perform LVC and balancing are easily available on shoppee (make sure you get the right sort for your cell chemistry). If you can’t find a suitable charger, just buy a buck (or boost) converter module with an adjustable current limit. Set the output voltage to somewhat less than 4.2V/cell - perhaps 3.9 or 4.0 - and the current limit to 0.5C. Power the input from any wall-wart that you have hanging around. Do not attempt to charge to 4.2V/cell with this jury-rigged setup - because it cannot perform charge termination, and cell balancers are usually a bit crap, it may easily overcharge one or more cells, resulting in bad things.


I’m going to go look for another battery. What happened is that I did not solder the wires to each cell, I simply squeezed it between the cells, thinking it would work fine. I connected the cells to where it belongs on the bms, and then connected it to the laptop, and it would charge just fine. However a wire came loose meaning the bms was without power briefly, and many bms will register that as a fault and permanently brick the bms, and needing the expensive nlba (or whatever) device to reset. Or I could have accidentally shorted something while trying to remove the old cells.

I just want to know if generic laptop bms exists, as the connections seems to be fairly standard.

Anyways I threw the whole bms in the trash, got tired of staying up until 5 am to deal with it. Plus soldering nickel strips rather than welding adds a few mm to the cell, and it would not fit in the enclosure at all.

I hate that they make these batteries so damn complicated. The laptop battery bms is a black box, nobody on the internet knows anything about it.

Sustainability my ass, nobody really cares about that. Especially with the advent of laptops where both ram and storage are fixed to the motherboard and cannot be changed without expensive equipment.

I found cheaper laptop battery on taobao for my laptop. I also got a box that can turn those 18650 cells into a power bank. I don’t know if a pd USB c exists that can output 20 volts so I can use it to power a laptop off a power bank.

Battery arrived, it works. I’ll know better than to monkey around with laptop BMS from now on. They basically just kill itself, or the BMS was already dead to begin with.

Because I took the cells from the old laptop battery, and used it inside a 18650 battery box (this is a box that turns your 18650 cells into a power brick). It charges/discharge fine, and has quite a bit of capacity on it…